Failure to adopt primary technology is an issue

Action Points

Note that this analysis of NHANES data suggests that many labs have difficulty detecting low, but present, blood lead levels in children.

This poses some risk as an acceptable lower threshold for blood lead has not yet been established.

Lower limits of detection for blood lead levels in children continue to provide measurement challenges to laboratories, a review of CDC data found.

A review of 5 years of results for target blood lead values found 40% of tests reported a "non-detectable" result at a target blood lead level of 1.48 μg/dL compared with only 5.5% unable to identify results when the blood lead level was 4.60 μg/dL, reported Kathleen L. Caldwell, PhD, of the CDC in Atlanta, and colleagues.

The amount of lead in children's blood has gone down over the years, making it more difficult to detect, they wrote in Pediatrics, In 2012, the CDC's Advisory Committee on Childhood Lead Poisoning Prevention recommended a population-based lead reference value of 5 μg/dL. They said this was calculated as the 97.5th percentile of blood lead in children ages 1 to 5 years in the U.S., based on the 2007-2010 National Health and Nutrition Examination Survey (NHANES) data, and was to be updated every 4 years.

Using NHANES data from 2011 to 2014, the researchers calculated the 97.5th percentile at 3.48 μg/dL, which is around 30% lower than the current reference value because the CDC has not made a final decision about changing the current reference value of 5 μg/dL.

Overall, there were more total lot screening failures due to "unacceptable lead contamination" due to the lower levels of detection. The authors noted that in the 2009-2010 NHANES, the mean blood lead level of 1.17 μg/dL with a level of detection of 0.3 μg/dL, less than 1% of screened lots failed. By contrast, there was a 35% failure rate in a blood lead level of detection of 0.07 μg/dL.

Lead and Multi-element Proficiency (LAMP) challenge results found "acceptable performance" for all participating laboratories, with around 60% of laboratories reporting "actual values" at ≤1.48 μg/dL, the authors said.

These new lower blood lead levels provide challenges for laboratories who will need to "accurately measure concentrations below their current [limits of detection.]" Recent FDA investigations have found deficiencies in certain tests used to measure blood lead levels in children.

When examining the children likely to be at or above the 90% percentile for blood lead levels, the authors found they were more likely to be less than age 3 years and living in low-income households (<$20,000). They added that while it was not significant, the proportion of boys and non-Hispanic blacks with blood lead levels above the 97.5th percentile was greater than those lower than the 97.5th percentile. This suggests "lead-based paint hazards continue to be a source of childhood lead exposure," they wrote.

In an accompanying editorial, Bruce Lanphear, MD, of Simon Fraser University in Vancouver, commented that despite these overall declines in children's blood lead levels over the years, pediatricians continue to treat cases of lead poisoning in this population. He argued that "failure to adopt or use primary technology" is the main reason for the continuing epidemic.

"We have failed to promulgate scientifically based environmental standards for lead in housing, soil, and water ... to deploy lead sampling tools to identify lead hazards before a child is exposed; and ... to eliminate recognized lead hazards and ban nonessential uses of lead," Lanphear wrote.

Caldwell's group highlighted the role that laboratories can play in improving their accuracy, advising that laboratories "consider various modifications, including selecting the optimal analytical method and testing for lead contamination of laboratory reagents and supplies used in the laboratory."

Lanphear also pointed to an American Academy of Pediatrics policy statement that recommends screening children's environments to identify potential lead in the house dust, soil, or water.

"Pediatricians can advocate for regulations to inspect and abate lead hazards in older housing before occupancy or during renovations, replace lead service lines ... and can ... advocate for regulations to protect children from toxic chemicals as well as chemicals of unknown toxicity," Lanphear argued.

Caldwell and co-authors disclosed no relevant relationships with industry.

Lanphear disclosed relevant relationships with the U.S. Environmental Protection Agency, the NIH, and the California Department of Toxic Substance Control, and testifying as an expert witness in several lead poisoning trials.

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